Pressure sensors are widely used for the analysis and monitoring of the pressure distribution on an object's surface subjected to the flow of fluid such as liquid and/or gas. For example, pressure sensors may be adjusted on an aircraft's airfoil to provide the pilot or manufacturer of the same aircraft with information about the airfoil's pressure distribution for monitoring and analysis. Moreover, pressure sensors can be used as an engineering tool to optimize the aerodynamic and/or hydrodynamic properties of an object's surface according to predetermined criteria. For example, information received from the pressure sensors arranged on a vehicle may be analyzed to derive the drag exerted by, e.g., air, on the vehicle in motion, and in particular, to determine which areas of the vehicle's surface are subjected to the highest drag and should therefore be reshaped to lower the vehicle's drag below a predetermined threshold value.
It should be noted that the pressure measured by such a pressure sensor may be the equivalent of the sum of dynamic pressure and/or static pressure acting on the object's surface.
Pressures measurement devices and systems as used in the art are outlined hereinafter. With reference to FIG. 1, a pressure measurement device and system 100 as used in the art includes a pressure transducer unit 120 comprising an array of pressure transducers 121 to measure the pressure a fluid exerts on a surface 141 of an object 140. To enable the measurement of the pressure, object 140 comprises measuring taps 142, to which at least some of the pressure transducers 121 are respectively coupled via a tube 143, which are pressed and/or glued or otherwise fixedly inserted into holes 144. Some of the fluid flowing over surface 141 exerts dynamic pressure thereon and engages therefore with measuring taps 142. Consequently, some fluid flows through the respective tubes 143 towards the corresponding member 122 of the transducer array 121 and exerts a pressure on the pressure sensor which is operatively coupled to member 122. The pressure exhibited by the fluid on the pressure sensor of member 122 depends, inter alia, on the velocity of the fluid, which is schematically indicated with arrow “V”, flowing over surface 141. As is known from thermodynamics, an increase in fluid velocity may for example result in a expansion of the fluid flowing over surface 141 (a physical phenomenon described, e.g., by means of the Bernoulli equation), whereby the increase in expansion may result in a decrease of the pressure exerted by the fluid in tube 143 and thus on the respective pressure sensor of transducer member 122. In the art, a pressure transducer unit 110 may be embodied by a single pressure transducer (not shown) which is operatively couplable to measuring tap 142 for the measurement of pressure on surface 141 on the respective location. The outer diameter of tubes 143 might be around 2 mm, whereas taps 142 may have an outer diameter of approx. 1 mm. The diameter of the channel of tap 142 can be as small 0.1 mm. Other pressure measurement devices as used in the art are outlined hereinafter.
U.S. Pat. No. 5,359,887, which is incorporated herein by reference in its entirety, discloses a coating material for wind tunnel luminescent barometry of surfaces such as airfoils and airframes uses a resin such as poly[1-(trimethylsilyl)propyne], or a siloxane polymer, to carry a pressure indicator. The pressure indicator may be photoluminescent ruthenium complex, such as [Ru(Ph2phen)2]Cl2, a photoluminescent platinum complex, such as PtOEP, and photoluminescent mixtures of pyrene and perylene.
U.S. Pat. No. 5,983,727, which is incorporated herein by reference in its entirety, discloses a fluid pressure sensor/sensor array having a substantially incompressible mounting structure with a cavity formed therein. An elastic membrane is attached to said mounting structure and across said cavity, separating the cavity from the fluid to be measured. At least one non-contact transducer is attached to the mounting structure in the cavity to detect deflection at a selected plurality of regions on the membrane. The sensitivity and pressure range of the sensor can be chosen by preselecting the elasticity of the membrane, stretching the membrane across the cavity under a preselected tension, maintaining a predetermined reference pressure in the cavity, and/or actively controlling the membrane tension. For a pressure sensor array, there are at least two fluid pressure sensors, where at least one sensor is of the type described herein. A sensor array can also be formed by multiple cavities within a single mounting structure.
U.S. Pat. No. 6,662,647, which is incorporated herein by reference in its entirety, discloses a gaseous fluid data sensor assembly for acquiring data regarding the ambient environment adjacent a surface of an airframe with adjacent air speeds below 40 knots (or another aerodynamic structure with low speed gaseous fluid flow adjacent thereto) having a flexible substrate adhesively conforming to the airframe surface, a conformable cover layer and a relatively thin air data sensor for measuring air pressure between the substrate and the cover layer. The assembly also includes a fiber optic communication link, a battery, a data acquisition subsystem, and a flexible printed circuit, all between the substrate and the cover layer. The cover layer is formed of a polymer film.
U.S. Pat. No. 6,826,968, which is incorporated herein by reference in its entirety, discloses a device for detecting the pressure exerted at different points of a flexible and/or pliable object that may assume different shapes. The device includes a plurality of capacitive pressure sensors and at least a system for biasing and reading the capacitance of the sensors. The requirements of flexibility or pliability are satisfied by capacitive pressure sensors formed by two orthogonal sets of parallel or substantially parallel electrodes spaced, at least at each crossing between an electrode of one set and an electrode of the other set, by an elastically compressible dielectric, forming an array of pressure sensing pixel capacitors. The system for biasing and reading the capacitance includes column plate electrode selection circuits and row plate electrode selection circuits and a logic circuit for sequentially scanning the pixel capacitors and outputting pixel values of the pressure for reconstructing a distribution map of the pressure over the area of the array.
U.S. Pat. No. 7,127,948, which is incorporated herein by reference in its entirety, discloses a sensor, sensory array, and associated method for measuring a pressure, wherein the sensor includes a piezoelectric sensory device that is disposed on an electrically insulative substrate that can be adhered to a member for measuring the pressure on the member. The piezoelectric sensory device defines first and second contact surfaces and is adapted to provide an electric potential between the surfaces that corresponds to a pressure on the piezoelectric sensory device. Conductive terminals are in electrical communication with the piezoelectric sensory device and therefore also provide the electric potential indicative of the pressure on the surface of the test member. An electrically insulative sheet is disposed opposite the piezoelectric sensory device from the substrate. An electronic monitoring device can be electrically connected to the piezoelectric sensory device via the terminals and configured to monitor the electric potential provided by the piezoelectric sensory device.
Xiao et al. describe in “A Pressure Sensor Using Flip-Chip on Low-Cost Flexible Substrate”, published in IEEE 2001 Electronic Components and Technology Conference, which is incorporated herein by reference in its entirety, a pressure sensor and an actuator which were assembled on a flexible substrate using FCOF technology, and a photolithography process allegedly meeting the solder bump fabrication requirement of the sensor chip.